The present invention relates to an inkjet printer which performs printing by moving an inkjet printhead relatively to a print medium, and a method and apparatus for controlling the inkjet printer.
An inkjet printer, which prints an image on print paper by scanning an inkjet head having a plurality of nozzles, employs a multi-pass printing method which reciprocally scans the inkjet head plural numbers of times for printing one area in order to achieve high-quality printing.
An inkjet printer of this type, which prints an image by reciprocally scanning a printhead, is known to cause a deviation cockling of a dot position depending on the printhead""s scanning direction at the time of discharging an ink droplet from the printhead onto a print medium, due to variations of a space between the printhead and a print medium such as a print sheet. It is also a known fact that, when an ink droplet (main ink droplet) is discharged from the inkjet printhead, a droplet called a satellite is discharged posterior to the main ink droplet, and recorded as a satellite dot on the periphery of a main dot recorded by the main ink droplet. The apparatus is usually adjusted so that the satellite dot is recorded over the main dot. However, there is a possibility that the positions of the main dot and satellite dot may deviate under various conditions.
While such problems occur, if printing is performed in one direction, the position where cockling occurs or the position where the satellite dot is printed is usually kept in one direction. Therefore, dot uniformity of a printed image is maintained to a certain degree. However, in a case where an image is printed by reciprocal scanning of a printhead in multi-pass printing for the purpose of print-time reduction, the aforementioned position where cockling occurs or the position where the satellite dot is printed differs in the forward scan and returning (backward) scan, causing to lose uniformity of an image.
The present invention has been proposed in view of the foregoing conventional example, and has as its object to provide an inkjet printer which enables to print a high-quality image by eliminating an influence of the aforementioned cockling or satellite or the like when an image is printed by multi-pass printing where an inkjet printhead is reciprocally scanned, and to provide a method and apparatus for controlling the inkjet printer.
Another object of the present invention is to provide an inkjet printer, and a method and apparatus for controlling the inkjet printer such that printing is performed while a printhead scans in a predetermined direction in accordance with the type of an image, so as to reproduce clear edges of an image, such as a character or the like.
Furthermore, another object of the present invention is to provide an inkjet printer, and a method and apparatus for controlling the inkjet printer which enables high-quality image printing by printing a relatively light portion of an image, where print dots are distributed, while a printhead scans in one direction, and printing a high-density portion of an image, where dots are dense, while the printhead scans reciprocally.
According to the present invention, the foregoing objects are attained by providing an inkjet printer for scanning an inkjet head having a plurality of nozzles arrayed in a first direction, in a second direction crossing the first direction, and for printing an image on a print medium in relative scanning of the inkjet head, comprising determination means for determining whether or not a density value of an image data is higher than a predetermined value, and selection means for selecting either a first print mode or a second print mode, wherein in the first print mode, printing is performed in bi-directional scanning and in the second print mode, printing is performed in unidirectional scanning, wherein in a case where the determination means determines the density value of the image data is higher than the predetermined value, the selection means selects the first print mode, and in a case where the determination means determines the density value of the image data is not higher than the predetermined value, the selection means selects the second print mode.
According to the present invention, the foregoing objects are attained by providing an inkjet printing method for scanning an inkjet head having a plurality of nozzles arrayed in a first direction, in a second direction crossing the first direction, and for printing an image on a print medium in relative scanning of the inkjet head, comprising a determination step of determining whether or not a density value of an image data is higher than a predetermined value, and a selection step of selecting either a first print mode or a second print mode, wherein in the first print mode, printing is performed in bi-directional scanning and in the second print mode, printing is performed in unidirectional scanning, wherein in a case where in the determination step, it is determined that the density value of the image data is higher than the predetermined value, in the selection step, the first print mode is selected, and in a case where in the determination step, it is determined that the density value of the image data is not higher than the predetermined value, in the selection step, the second print mode is selected.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.